Ionization apparatus



Feb.20,196s @Hm ETAL 3,370,200

IONIZATION APPARATUS Filed Jan. 50, 1963 TNVENToRs;

GERHARD HET/L, GNTER LTTGE/vs.v

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f M 5% ATTORNEYS United States Patent O 3,370,200 IONIZATION APPARATUS Gerhard Heyl, Cologne, Stammheim, and Gnter Lttgens, Leverkusen, Germany, assignors to Farbenfabriken Bayer Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany Filed' Jan. 30, 1963, Ser. No. 254,918 Claims priority, application Germany, Feb. 10, 1962, F 35,999 2 Claims. (Cl. 317-4) The invention relates to an ionization apparatus equipped with spray elements which are connected to a high voltage source through a protective resistance. The air surrounding an electrostatically charged body is ionized by the corona discharge at the spray elements (wires or clips) of such instruments. The body attracts to itself ions of the opposite sign until its charge is neutralized. In known forms of construction, a protective resistance which limits the current flowing when the spray elements are touched is built into the high voltage producing system in order to protect the operators. A disadvantage of this arrangement is that a voltage loss occurs at the protective resistance built into the high voltage conductor. This voltage loss is produced by the insulation currents flowing in the cable and in the ionization apparatus and by the ionic current tiowing through the spray elements.

Another disadvantage is that the protection against contact with the spray elements provided by the protective resistance built into the supply cable is not adequate This cable represents a capacitance which is charged to the operative voltage of the ionization apparatus (condenser effect). When any current conducting parts of the ionization apparatus are touched, this condenser is discharged and this may cause the ow of electric currents that are harmful to health. Even when current impulses are produced that are not sufficiently powerful to be dangerous, the person coming into contact with this impulse `may suffer a secondary accident as a result of shock.

Two calculations will be given by way of example to explain the principle.

EXAMPLE 1 When an ionization apparatus l meter in length has an insulation resistance of 108 ohm (this resistance depending among other factors on the conditions of the surrounding atmosphere), the high voltage transformer delivers 104 v. and the protective resistor which limits the current to 5 l0"4 a. when contact is made has a resistance of 5 107 ohm, a voltage drop of 5 l03 v. occurs at this protective resistor due to the insulation current of l4 a. To this is added the voltage loss of about l03 volt caused by the ionic current. Less than half the voltage produced is therefore available at the spray elements. As the insulation resistance varies considerably over a period, for example due to dirt or variations in the humidity of the atmosphere, the voltage actually available at the spray elements will also vary and hence the effectiveness of the instrument will vary in a manner which is quite uncontrollable.

EXAMPLE 2 A shielded high voltage cable has a capacity of about 2 l010 f./m. When this cable is used for a 5 rn. long conductor leading to an ionization apparatus which is operated at l04 v., the energy stored in the cable capacitance is 5 10-2 watt seconds. When a condenser of 10-9 f. charged to 104 volt is discharged, for example through the hand, this is very unpleasant and may produce a shock.

These disadvantages may be avoided by assembling the protective resistor in accordance with the invention directly on the spray elements in the tube.

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Several separate and equal protective resistors may be used for a small number of spray clips or spray wires arranged in groups. The spray elements of a group supplied by one protective resistor must, of course, be nsulated against the spray elements of adjacent groups.

The above disadvantages inherent in communal protective resistors in high voltage producing systems may thereby be avoided. This will be explained with reference to an example.

If, in the l m. ionization apparatus described in Example l, protective resistors of 5 l0'I ohm each are provided for each 10 centrimetre portion, only the insulation current of one spray rod unit will ow over each of these resistors. This portion is less than l/lo of the insulation current in Example 1 because, for example, the insulation currents in the cable no longer flow through the preliminary resistors. There Will therefore be a voltage loss of only 5 l02 v. The voltage variation due to alteration in the insulation resistance is correspondingly reduced to less than 1/10. The voltage loss due to the ionization current is reduced to 1/10. The efliciency becomes largely independent of dirt and atmospheric humidity. The instrument supplying the current can be designed for a smaller voltage. This system of protective resistors has the fur- -ther advantage that, for example, in the event of a short circuit due to touching one of the tips, only a small portion of the ionization apparatus will fall out of action.

As the protective resistor is installed directly in the ionization apparatus, even the current flowing as a result of the charged cable capacitance when contact is accidentally made will not be higher than 5 l04 a. A current impulse due to discharge of a capacitance will no longer occur because the capacitance discharged on contact is negligible.

In some cases it may be advantageous to install a smaller common protective resistor in the voltage producing apparatus in addition to the individual resistance for the purpose of protecting the transformer. The resistance of this protective resistor may be 10 to 100 times smaller than the resistances in the ionization apparatus since it is not designed to protect the operators against excessive currents flowing in the event of contact but to protect the transformer against overloading. The same effect may be achieved also with a scatter field transformer used as high voltage source. j

It is particularly advantageous to apply the invention to a building block system. FIGURES 1 and 2 illustrate a building block. The spray rod is composed of individual identical parts 5 to 25 cm., preferably l0 cm. in length. The insulating rod 2 has two bores and a groove 8 cut into it in which a metal plate 7 containing the spray tips 9 is inserted. One bore takes the high voltage supply 3 and the other the preliminary resistor 6 which is connected at one end with the high voltage supply 3 and at the other end with the plate 7. The groove 8 is filled with casting resin to such an extent that the spray tips 9 project by about 3 mm. The bore for the resistor 6 is closed with two plugs 4 and 5 of casting resin or wax. The individual rod elements are pushed into a metal tube 1 of the desired length which acts at the same time as a grounded counterelectrode for the spray tips. When they are assembled, the voltage supplies of the rod elements are joined together. The tube 1 is closed at both ends with caps (not shown), and the high voltage cable is lixed at one end and a blank flange at the other.

The principle of the invention may be applied to ionization apparatuses that are operated with direct current or low or high frequency alternating current.

We claim:

1. An ionization apparatus which comprises a body of electrical insulation material, a first electrically conductive member supported by said insulation body, at least one discharge electrode conductively connected to said rst member and extending therefrom, a second elec trically conductive member extending within said insulation body and disposed for connection to a terminal of an external high voltage electrical source, a resistor disposed within said insulation body for support thereby and electrically connected to said first and second conductive members to limit electrical current flow therebetween, and a third electrically conductive member supported by said insulation body and disposed for connection to another terminal of said high voltage source, said third member being disposed in spaced apart relation to each discharge electrode extending from said first member to accommodate an electrical ionization discharge therebetween when said second and third members are connected to terminals of the high voltage source having a potential diierence suflicient to effect such ionization discharge, with the current flow during said ionization discharge being limited by said resistor.

2. The apparatus according to claim 1 wherein said insulation body is cylindrical, and said rst member extends longitudinally within said insulation body with each discharge electrode projecting outwardly with respect thereto, and said third member is a cylindrical sheath disposed in contact with the exterior surface of the cylindrical insulation body for support thereby, and having a longitudinally extending cut-away portion delining edges disposed in spaced-apart relation to said projecting electrodes to accommodate electrical ionization discharge between each electrode and said edges.

References Cited MILTON O. HIRSHFIELD, Primaly Examiner.

20 SAMUEL BERNSTEIN, Examiner.

D. YUSKO, I. SILVERMAN, Assistant Examiners. 

1. AN IONIZATION APPARATUS WHICH COMPRISES A BODY OF ELECTRICAL INSULATION MATERIAL, A FIRST ELECTRICALLY CONDUCTIVE MEMBER SUPPORTED BY SAID INSULATION BODY, AT LEAST ONE DISCHARGE ELECTRODE CONDUCTIVELY CONNECTED TO SAID FIRST MEMBER AND EXTENDING THEREFROM, A SECOND ELECTRICALLY CONDUCTIVE MEMBER EXTENDING WITHIN SAID INSULATION BODY AND DISPOSED FOR CONNECTION TO A TERMINAL OF AN EXTERNAL HIGH VOLTAGE ELECTRICAL SOURCE, A RESISTOR DISPOSED WITHIN SAID INSULATION BODY FOR SUPPORTING THEREBY AND ELECTRICALLY CONNECTED TO SAID FIRST AND SECOND CONDUCTIVE MEMBERS TO LIMIT ELECTRICAL CURRENT FLOW THEREBETWEEN AND A THIRD ELECTRICALLY CONDUCTIVE MEMBER SUPPORTED BY SAID INSULATION BODY AND DISPOSED FOR CONNECTION TO ANOTHER TERMINAL OF SAID HIGH VOLTAGE SOURCE, SAID THIRD MEMBER BEING DISPOSED IN SPACED APART RELATION TO EACH DISCHARGE ELECTRODE EXTENDING FROM SAID FIRST MEMBER TO ACCOMMODATE AN ELECTRICAL IONIZATION DISCHARGE THEREBE- 